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iscsi-target: Fix race with thread_pre_handler flush_signals + ISCSI_THREAD_SET_DIE 

This patch addresses an long standing race in iscsi_[rx,tx]_thread_pre_handler()
use of flush_signals(), and between iscsi_deallocate_extra_thread_sets() setting
ISCSI_THREAD_SET_DIE before calling kthread_stop().

It addresses the issue by both holding ts_state_lock before calling send_sig()
in iscsi_deallocate_extra_thread_sets(), as well as only calling flush_signals()
when ts->status != ISCSI_THREAD_SET_DIE within iscsi_[rx,tx]_thread_pre_handler()
code.

v2 changes:
  - Add explicit complete(&ts->[rx,tx]_start_comp); before kthread_stop() in
    iscsi_deallocate_extra_thread_sets()
  - Drop left-over send_sig() calls in iscsi_deallocate_extra_thread_sets()
  - Add kthread_should_stop() check in iscsi_signal_thread_pre_handler()

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2013-09-06 20:46:50 -07:00
parent 0105c257be
commit d5705c4ab5
1 changed files with 13 additions and 6 deletions
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19
drivers/target/iscsi/iscsi_target_tq.c
View File

@ -189,16 +189,20 @@ static void iscsi_deallocate_extra_thread_sets(void)
spin_lock_bh(&ts->ts_state_lock);
ts->status = ISCSI_THREAD_SET_DIE;
spin_unlock_bh(&ts->ts_state_lock);
if (ts->rx_thread) {
send_sig(SIGINT, ts->rx_thread, 1);
complete(&ts->rx_start_comp);
spin_unlock_bh(&ts->ts_state_lock);
kthread_stop(ts->rx_thread);
spin_lock_bh(&ts->ts_state_lock);
}
if (ts->tx_thread) {
send_sig(SIGINT, ts->tx_thread, 1);
complete(&ts->tx_start_comp);
spin_unlock_bh(&ts->ts_state_lock);
kthread_stop(ts->tx_thread);
spin_lock_bh(&ts->ts_state_lock);
}
spin_unlock_bh(&ts->ts_state_lock);
/*
* Release this thread_id in the thread_set_bitmap
*/
@ -400,7 +404,8 @@ static void iscsi_check_to_add_additional_sets(void)
static int iscsi_signal_thread_pre_handler(struct iscsi_thread_set *ts)
{
spin_lock_bh(&ts->ts_state_lock);
if ((ts->status == ISCSI_THREAD_SET_DIE) || signal_pending(current)) {
if (ts->status == ISCSI_THREAD_SET_DIE || kthread_should_stop() ||
signal_pending(current)) {
spin_unlock_bh(&ts->ts_state_lock);
return -1;
}
@ -419,7 +424,8 @@ struct iscsi_conn *iscsi_rx_thread_pre_handler(struct iscsi_thread_set *ts)
goto sleep;
}
flush_signals(current);
if (ts->status != ISCSI_THREAD_SET_DIE)
flush_signals(current);
if (ts->delay_inactive && (--ts->thread_count == 0)) {
spin_unlock_bh(&ts->ts_state_lock);
@ -472,7 +478,8 @@ struct iscsi_conn *iscsi_tx_thread_pre_handler(struct iscsi_thread_set *ts)
goto sleep;
}
flush_signals(current);
if (ts->status != ISCSI_THREAD_SET_DIE)
flush_signals(current);
if (ts->delay_inactive && (--ts->thread_count == 0)) {
spin_unlock_bh(&ts->ts_state_lock);